temp2raw: Converts temperature (oC) to raw thermal data

Description Usage Arguments Details Value Author(s) References See Also Examples

View source: R/temp2raw.R

Description

Inverse of the function raw2temp. Typically used when incorrect settings were used during thermal imaging analysis, and the raw values need to be extracted in order to re-calculate temperature using raw2temp. Parameters under which the temperatures were estimated should be known, since the conversion to raw will take those into account.

Usage

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temp2raw(temp, E = 1, OD = 1, RTemp = 20, ATemp = RTemp, IRWTemp = RTemp, IRT = 1, 
RH = 50, PR1 = 21106.77, PB = 1501, PF = 1, PO = -7340, PR2 = 0.012545258)

Arguments

temp

estimate temperature (oC) from an infrared thermal imaging file

E

Emissivity - default 1, should be ~0.95 to 0.97 depending on object of interest. Determined by user.

OD

Object distance from thermal camera in metres

RTemp

Apparent reflected temperature (oC) of the enrivonment impinging on the object of interest - one value from FLIR file (oC), default 20C.

ATemp

Atmospheric temperature (oC) for infrared tranmission loss - one value from FLIR file (oC) - default value is set to be equal to the reflected temperature. Transmission loss is a function of absolute humidity in the air.

IRWTemp

Infrared Window Temperature (oC). Default is set to be equivalent to reflected temp (oC).

IRT

Infrared Window transmission - default is set to 1.0. Likely ~0.95-0.97. Should be empirically determined. Germanium windows with anti-reflective coating typically have IRTs ~0.95-0.97.

RH

Relative humidity expressed as percent. Default value is 50.

PR1

PlanckR1 - a calibration constant for FLIR cameras

PB

PlanckB - a calibration constant for FLIR cameras

PF

PlanckF - a calibration constant for FLIR cameras

PO

PlanckO - a calibration constant for FLIR cameras

PR2

PlanckR2 - a calibration constant for FLIR cameras

Details

Note: PR1, PR2, PB, PF, and PO are specific to each camera and result from the calibration at factory of the camera's Raw data signal recording from a blackbody radiation source. Sample calibration constants for three different cameras (FLIR SC660 with 24x18 degree lens, FLIR T300 with 25x19 degree lens, FLIR T300 with 2xtelephoto.

Calibration Constants by cameras: SC660, T300(25o), T300(25o with telephoto)

Constant FLIR SC660 FLIR T300 FLIR T300(t)
PR1: 21106.77 14364.633 14906.216
PB: 1501 1385.4 1396.5
PF: 1 1 1
PO: -7340 -5753 -7261
PR2: 0.012545258 0.010603162 0.010956882

PR1: PlanckR1 calibration constant PB: PlanckB calibration constant PF: PlanckF calibration constant PO: PlanckO calibration constant PR2: PlanckR2 calibration constant

The calibration constants allow for the raw digital signal conversion to and from the predicted radiance of a blackbody, using the standard equation:

temperature<-PB/log(PR1/(PR2*(raw+PO))+PF)-273.15

Also used in calculations for transmission loss are the following constants:

ATA1: Atmospheric Trans Alpha 1 0.006569

ATA2: Atmospheric Trans Alpha 2 0.012620

ATB1: Atmospheric Trans Beta 1 -0.002276

ATB2: Atmospheric Trans Beta 2 -0.006670

ATX: Atmospheric Trans X 1.900000

Value

Returns numeric value. Can handle vector or matrix objects

Author(s)

Glenn J. Tattersall

References

1. http://130.15.24.88/exiftool/forum/index.php/topic,4898.60.html

2. Minkina, W. and Dudzik, S. 2009. Infrared Thermography: Errors and Uncertainties. Wiley Press, 192 pp.

See Also

raw2temp

Examples

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# General Usage:
# temp2raw(temp,E,OD,RTemp,ATemp,IRWTemp,IRT,RH,PR1,PB,PF,PO,PR2)

# Example with all settings at default/blackbody levels:
temp2raw(23,1,0,20,20,20,1,50,PR1=21106.77,PB=1501,PF=1,PO=-7340,PR2=0.012545258)

# Example with emissivity=0.95, distance=1m, window transmission=0.96, all temperatures=20C,
# 50 RH:

temp2raw(23,0.95,1,20,20,20,0.96,50) 
# Note: default calibration constants for my FLIR camera will be used if you leave out the
# calibration data

t<-10:50
r1.0<-temp2raw(t,1,0,20,20,20,0.96,50)
r0.9<-temp2raw(t,0.9,0,20,20,20,0.96,50)

dev.off()
plot(t,r1.0,type="l",col="red")
lines(t,r0.9,col="black")
legend("topleft", bty = "n", c("E=1.0", "E=0.9"), lty=c(1,1), col=c("red", "black"))

Thermimage documentation built on May 29, 2017, 6:47 p.m.

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